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Entity Relationship Diagrams
Entity “An entity is a business object that represents a group, or category of data.”1 Do we know a similar concept? 1) Stephens, R.K. and Plew. R.R., Database Design. SAMS, Indianapolis , IN.
Attribute “An attribute is a sub-group of information within an entity.”1 Do we know a similar concept? 1) Stephens, R.K. and Plew. R.R., Database Design. SAMS, Indianapolis , IN.
Entity Relationship ModelsMandatory Relationships Optional Relationships Many-to-Many Relationships One-to-Many Relationships One-to-One Relationships Recursive Relationships
Mandatory, Many-to-ManyINSTRUCTOR STUDENT INSTRUCTOR STUDENT
Optional, Many-to-ManyDEPARTMENT STUDENT DEPARTMENT STUDENT
Optional/Mandatory, Many-to-ManyINSTRUCTOR SKILL INSTRUCTOR SKILL
Optional/Mandatory, One-to-ManyPRODUCT VENDOR PRODUCT VENDOR
Mandatory, One-to-One AUTOMOBILE ENGINE AUTOMOBILE ENGINE
Recursive EMPLOYEE supervises is supervised by
Resolving Many-to-Many RelationshipsMany-to-many relationships should be avoided. We can resolve a many-to-many relationship by dividing it into two one-to-many relationships.
Resolving Many-to-Many RelationshipsSALES ORDERS INV. ITEMS SALES ORDERS INV. ITEMS ORDER ITEMS
Example (ER Diagram) SALES ORDERS INV. ITEMS ORDER ITEMS CLERKSCUSTOMERS
ER Modeling Case Studies
Entity Relationship (E-R) Modeling
Slide 1 Insert your own content. Slide 2 Insert your own content.
E-R Model (1) IS 240 – Database Management Lecture #5 – Prof. M. E. Kabay, PhD, CISSP Norwich University
Author: Graeme C. Simsion and Graham C. Witt Chapter 8 Organizing the Data Modeling Task.
Author: Graeme C. Simsion and Graham C. Witt Chapter 6 Primary Keys and Identity.
Author: Graeme C. Simsion and Graham C. Witt Chapter 4 Subtypes & Supertypes.
0 - 0.
DIVIDING INTEGERS 1. IF THE SIGNS ARE THE SAME THE ANSWER IS POSITIVE 2. IF THE SIGNS ARE DIFFERENT THE ANSWER IS NEGATIVE.
Introduction to SQL 1 Lecture 5. Introduction to SQL 2 Note in different implementations the syntax might slightly differ different features might be.
Advantages and disadvantages, architectures and data models
Conceptual / semantic modelling
Problem # Problem #
5.9 + = 10 a)3.6 b)4.1 c)5.3 Question 1: Good Answer!! Well Done!! = 10 Question 1:
1 SA0951a Entity-Relationship Modelling. 2 What is it about? ER model is used to show the Conceptual schema of an organisation. Independent of specific.
Conceptual Design using the Entity-Relationship Model
Transform an ER Model into a Relational Database Schema
Week 5 Relational Database Design by ER- -to-Relational Mapping.
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